1. Field of the Invention
This invention relates to an image pickup device of the frame transfer type and an image pickup arrangement using this image pickup device of the frame transfer type which are suitable to picture a still image.
2. Description of the Prior Art
Generally, video signals of two so-called interlaced fields are required to obtain a still picture which is suitable for the standard television system using a solid state image pickup device.
However, with a CCD (charge coupled device) of the frame transfer type, such a readout method has been conventionally considered to be impossible. That is to say, referring to FIG. 1, there is shown a construction of a prior-art frame transfer type CCD, in which a reference numeral 1 denotes an image pickup array; 2 is a storage array; 3 is a horizontal transfer register as register means; 4 is an output amplifier; and 5 is a signal output terminal.
A reference character PS indicates a cell, and a plurality of such cells are arranged in rows and columns, thereby to constitute the image pickup array 1 and the storage array 2, respectively. Each cell PS has a charge transfer function in the vertical direction in the drawing and also has a horizontal transfer function in the horizontal transfer register 3.
Reference characters .phi..sub.1 -.phi..sub.3 represent transfer clocks of the image pickup array, storage array and horizontal transfer section, respectively.
The portion other than the image pickup array, i.e. the hatched portion is shielded against the light.
In the prior-art CCD with such a construction, the image information incident upon the image pickup array is sampled by each cell and accumulated as charge information.
Thereafter by supplying the clocks .phi..sub.1 -.phi..sub.3, the charge information of the image pickup array is transferred as it is to the storage array at high speed and is read out for a proper period of time.
Namely, after transferring the information of the storage array to the register 3 row by row, this row information is read out by the clock .phi..sub.3 for one horizontal scan period, thereby sequentially obtaining the scanning line signals corresponding to the standard television signals. However, since the interlace of 2:1 is done in the standard television system, the different locations on the monitor screen are scanned for playback with respect to the first and second fields. Therefore, unless the video signals of two fields which were mutually interlaced at the time of picturing are obtained, such problems will be caused as a picture blur occurring upon playback and the resolution being reduced, or the like.
However, in a conventional frame transfer type CCD with such a construction as shown in FIG. 1, it is impossible to individually read out the fields bearing odd numbers and the fields bearing even numbers in the screen which has been once pictured.